Bogging down on long ride

[weasley]

The KTM. I rode it all last year with no issue. Took it for a service a couple of weeks ago then didn’t ride it immediately. This weekend I went for a 100 mile ride on Friday, to a place that was booked to remap it to cure the usual KTM snatchy throttle and generally smooth it out. After about 70-80 minutes riding, it started to bog down if I opened the throttle fully in a high gear, such that it wouldn’t accelerate. If I eased off it would pick up again. No FI light, no stuttering or misfiring, just no drive.

It then got gradually worse until a couple of times it cut out. I was able to restart it immediately, before even coming to a stop and it would then go again but was still not pulling right. I got to my destination (hotel) and checked the obvious things. The only thing I found was a loose positive battery terminal, which I tightened. I took it for a test ride and it all felt ok, so that was that, I thought.

Next morning I took it to BSD Performance for the remap. I mentioned the running issue and battery thing. I also struggled to start it that morning due to a low battery, but it eventually got going.

They had it a couple of hours, did their thing and talked me through all the mapping changes - they never saw any running problems on the dyno or road tests and the dyno curve I have looks fine.

On the ride home, the same thing happened, after about the same time riding. I got it home and parked it and haven’t had a chance to investigate further, but I am thinking fuel starvation. Maybe a blocked filter or dodgy supply line? Or even the pump?

Any thoughts from the collective on this? Or experience of the same thing?
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[doggone]

Could it be simple vacuum lock, blocked breather in tank (a trapped pipe) ?
See if air rushes in if you slowly open it.
It's always tempting to leap to hasty conclusions if some work has been done.

[weasley]

I did think about that. The breather from the filler cap is clear and no noticeable ‘whoosh’ when opening it. Worth looking closer though when I take the tank off.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[St George]

Sounds like a carb issue, may need a clean out.

[grr666]

[Tankie]

Two stroke or four stroke ?
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Always learning, everyday is a school day

[Sister Sledge]

Does sound like fuel starvation. Sounds like it's slowly getting worse too.
Pump, fuel line/filter. That sort of thing.
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CCM 404 DS

[Robby]

The confusing thing is the lack of FI light illuminating.

I would expect to see the FI light coming on if there was a problem with fuel pressure or spark.

That said, I don't know if it has a fuel pressure sensor worked into the FI system or just a regulator.

Can you plug in a code reader? You can have a code stored without the FI light coming on.

[weasley]

4-stroke, fuel-injected, petrol.

Looking at parts diagrams I can’t find a fuel pressure regulator so assumed it was handled either by the pump or a simple pressure valve. Pretty sure there’s no pressure sensor.

KTM do some specialised diagnostic tools but I don’t have any. I would hope that BSD would have spotted any logged codes.

My concern about taking it to the KTM dealer that serviced it is that it takes over an hour to show up, and they are only 15 minutes away. I can imagine it would be one of those cases where nothing shows up under test and I get reamed for an investigation fee.

Hopefully I can at least have the tank off in the next day or two and see if anything obvious falls out - until then it’s all supposition and conjecture but I appreciate the input.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[weasley]

Ok, I thought I had solved this. I went to take the tank off today to investigate and found that both fuel stopcocks were closed. I assume the workshop forgot to open them after the service recently - it all adds up and I thought I had an easy fix.

Just to check I took it for a long ride. It was all good - no bogging, no hesitation no matter how I provoked it. Until I was about 2 miles from home on a stretch of dual carriageway that goes uphill. I opened it up up the hill and the hesitation came back. I’d done about 100 miles, so much further than when it showed up before, but there it was. Pin the throttle in any gear and it would get to around 8-9,000 rpm and then hesitate and not gain any more speed.

It would sort itself out for a bit after a stop but when I went back and tried again there it was again. No FI light, no other symptoms.

I have checked the battery - it’s charging at around 13.5v with the engine running.

Because I went for such a long ride I’ve run out of light to have the tank off tonight, so will have to get at it another time.

I wonder, would having the cocks shut have caused the fuel pump any issues? One of them was a small crack open so maybe enough to draw some fuel from one side.

I’m also wondering if the BSD mapping will have been affected by the taps. The dyno run was strong enough - 112 bhp and 70Nm with a decent shaped curve.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[P.addy]

Does it have secondary injectors? I've seen an R1 and my older CBR600RR do similar. Mine was injectors, think the R1 was butterfly not opening at 1/2 max revs.

[weasley]

It has two butterflies - one opened by cable from the throttle and the other controlled by the ECU. Their behaviour was part of the mapping that BSD carried out.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[weasley]

I changed the fuel filters today, which is not a straightforward task as it means having the whole fuel pump assembly out of the tank to then be disassembled and 2 filters, several o-rings, a spring and other rubber bushes replaced.

The pre-filter was very discoloured but the main paper filter was ruined and came apart in my hands. It looks like the bits stuck in the media are from the filter itself and have come from where the metal plates are (or were) stuck to the media - I suspect something in the fuel, maybe ethanol, has been eating away at it.

Maybe this is either the whole reason or part of the reason for the running issues? I have started it up and it runs ok but I haven’t test ridden it yet.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[Nobby the Bastard]